1. Field of the Invention
The present invention generally relates to devices used in the cleaning of heating, ventilation, and air conditioning (HVAC) apparatus, and more specifically, to a boiler cleaning apparatus and method for cleaning the external surfaces of water-tube heat exchangers.
2. Description of the Related Art
The exterior surfaces of heat exchange tubes in a heat recovery steam generator or HRSG are exposed to the byproducts of combusting fuel gases. These byproducts include but are not limited to soot, slag and ash that adhere to the surfaces of the tubes, creating a layer that inhibits the rate of heat transfer between the fluid (water and/or steam) flowing inside the tubes and the combusting gases flowing on the exterior of the tubes. A decrease of heat transfer efficiency demands the burning of more fuel to achieve a desired level of performance, thus diminishing the efficiency of the HRSG, increasing the costs of operation, and increasing emissions. Furthermore, the layer of byproducts may function to cause tube wall degradation leading to premature tube failure, and increased maintenance or replacement expense.
In the past in order to spread tubes of a vertical or horizontal tube bank during cleaning of a boiler apparatus, multiple hydraulic wedges were required to be installed in a sequence, combined with insertion of a blocking medium (typically wood blocks), to keep a temporary cleaning lane open between the tubes, while cleaning activities were performed between the tubes. The depth of penetration into the tube bank was limited to a few of the outer most tube rows, and the effectiveness of cleaning was diminished. Problems associated with the older tube spreading tooling include the flexure of the tines or bare tubes which occurred when attempting to spread apart tubes disposed at a distance away from the hydraulic ram. At some point of tube spreading, a risk is present of excessive flexure of outer rows of tubes when attempting to spread deeper tube rows, which in turn limits the available insertion depth into the tube bank for cleaning activities.
Another problem associated with the older tube spreading tooling is the weight of the tube spreading device, which may act as a limiting factor requiring multiple workers to fully operate the cleaning device.
An additional problem associated with the older tube spreading tooling includes the use of multiple blocks positioned between tubes which have been previously separated, to maintain space for temporary cleaning lanes. The use of multiple blocks consumes valuable space used by cleaning lances and/or cleaning tools or devices during cleaning operations. Cleaning activities in narrow vertical or horizontal lanes between rows of tubes is restricted as a result of the inherent thickness of multiple blocks stacked on top of each other, which in turn decreases the available surface area for cleaning, reducing cleaning effectiveness.
A further problem associated with the older tube spreading tooling is related to safety to service personnel, because the known tube spreading tooling including components such as an hydraulic hand pump, hydraulic wedge, and blocking, to name a few, while being used at heights, and in peculiar spaces proximate to the tubes of the boiler apparatus, proved difficult to safely control when utilizing wedges of increased length or size. For example a hydraulic hand pump used to activate a wedge would be difficult for a person to operate safely while located on temporary scaffolding.